Most conventional vehicles such as loaders or bulldozers are either driven by four wheels or by two tracks. Typical track-propelled vehicles employ a pair of spaced steel or rubber endless tracks that are driven to move the vehicle over the ground. Vehicles that are solely wheel-propelled typically include a pair of front wheels and a pair of rear wheels that are rotatably driven to propel the vehicle. The wheels of the wheel-propelled vehicles are generally large and have tread designs that aid in moving the vehicle over sand, clay and mud. These conventional vehicles, although capable of moving over terrain having a variety of soil conditions, frequently become stuck because all of the tractional forces and propelling surfaces are not always put to the ground.
Conventional four wheel vehicles and conventional two track vehicles often cause environmental damage when used in natural areas. Recently, environmental concerns have been raised about the disruption of the topsoil which occurs when conventional loader/bulldozer-type vehicles are operated on the topsoil, sand or other soft terrain of sensitive natural areas. For example, in the tree harvesting industry, construction industry and/or the agricultural industry, the operation of conventional vehicles of the type described may cause significant damage to the topsoil, which in turn may result in the formation of ruts which may lead to soil erosion.
U.S. Pat. No. 5,615,748 discloses a vehicle that has a central track and a pair of flanking wheels disposed on opposing sides of the track. The flanking wheels are mounted for pivotal movement about a pair of generally vertically extending axes. Turning the wheels about these axes steers the vehicle in a desired direction. The vehicle of the '748 patent helps overcome the problems associated with conventional vehicles by distributing its load over a large area, including the track and both tires. This help reduce the damage caused to the topsoil by the vehicle as it operates.
The manner in which the flanking wheels steer the vehicle disclosed in the '748 patent presents two problems. The first problem is that the turning radius for the vehicle is rather large and thus the vehicle needs a significant amount of room to make its turns. The second problem is that when the wheels are turned at an angle and power is still being supplied to the track, the tractive forces of the track applies a force against the axial face of the tires. As a result, the tires may become separated from their respective rims if the force applied by the track is sufficiently high.
Accordingly, there exists a need for a vehicle that has improved steering capabilities. To meet this need, one aspect of the present invention provides a vehicle comprising a main frame structure, a driving track assembly mounted with respect to the main frame structure, and a pair of secondary driving assemblies mounted on opposing lateral sides of the track assembly in flanking relation. The driving track assembly includes an endless ground engaging track that extends in a vehicle driving direction. Each of the secondary driving assemblies includes a ground engaging driving structure spaced laterally from the endless track. Preferably, the ground engaging structure of each secondary driving assembly is a rotating wheel.
An engine assembly is constructed and arranged to supply power to both the track assembly and the secondary driving assemblies. Preferably, the engine assembly includes an internal combustion engine that drives one or more hydraulic pumps. However, this aspect of the invention is not intended to be limited in such a manner. The driving track assembly moves the endless track using power supplied from the engine assembly to affect a vehicle driving operation wherein the endless track engages the ground to drive the vehicle in the vehicle driving direction. Each of the secondary driving assemblies operates the ground engaging driving structures using power supplied from the engine assembly so as to impart force to the vehicle in one of the vehicle driving direction and a vehicle reversing direction that extends generally opposite the vehicle driving direction. A steering device is operatively connected to the secondary driving assemblies and controls operation of the secondary driving assemblies so as to affect a vehicle steering operation wherein the force imparted to the vehicle by one of the ground engaging driving structures is greater than the force imparted to the vehicle by the other of the ground engaging driving structures, thereby causing the vehicle to turn with respect to the vehicle driving direction.
It can be appreciated that the use of ground engaging structures such as flanking wheels that impart different forces to the vehicle to affect vehicle steering are advantageous over wheels that turn about generally vertical axes because significantly less space is needed to turn the vehicle. Specifically, with the track stopped, the two ground engaging structures, preferably in the form of flanking wheels, can turn the vehicle in any direction with a minimal turning radius in comparison to pivoting wheels. This feature is particularly advantageous in applications such as harvesting row crops where a minimal turning radius is desired. In row crops, it is desired to maximize the crop size on any given plot of land and thus it is desirable to extend the rows as far as possible to the end of the plot. However, at each end of the rows sufficient room must be left for the harvesting vehicle to turn during harvesting operations. With conventional vehicles, a generous amount of space must be provided at the row ends to accommodate vehicle turning because of their large turning radius. The same holds true for the vehicle of the '748 patent. With a vehicle constructed in accordance with this aspect of the invention, the smaller turning radius means that less room is needed to turn the vehicle at the end of the crop rows. Thus, the crop rows can be extended further, thereby making more efficient use of the land.
Another problem with the vehicle of the '748 patent is that not all the tractive forces are applied to the ground when the vehicle is driving over uneven terrain. Specifically, when the vehicle drives over uneven terrain, one wheel may ride over a raised protrusion, such as a rock or a stump. As a result, in an embodiment where the wheel axles are rigidly mounted to the frame, the vehicle is lifted so that a portion of the track is lifted from the ground; and in an embodiment where the wheels are mounted on a single axle that moves vertically relative to the track, both wheels are raised vertically, thereby moving the opposite wheel out of contact with the ground. In either situation, there is a loss of contact between the vehicle's driving assemblies and the ground, thereby diminishing the vehicle's tractive and braking capabilities. Likewise, when the vehicle drives over uneven terrain with one of the wheels passing over a rut or depression in the ground, the wheel over the depression in either embodiment of the '748 patent vehicle will be out of ground contact.
Thus, there exists a need for a vehicle with a central track and a pair of secondary driving assemblies flanking the track in which the secondary driving assemblies are ensured of remaining in ground contact while the vehicle is driven over uneven terrain. To meet this need, another aspect of the present invention provides a vehicle comprising a main frame structure, a driving track assembly mounted with respect to the main frame structure, and a pair of secondary driving assemblies mounted on opposing lateral sides of the track assembly in flanking relation. The driving track assembly includes an endless ground engaging track that extends in a vehicle driving direction and a hydraulically powered motor constructed and arranged to drive the ground engaging track.
Each of the secondary driving assemblies comprises a vertically repositionable axle assembly mounted to the frame, a ground engaging driving structure mounted on the axle assembly, a hydraulically powered motor mounted to the axle assembly for generally vertical movement therewith, and a vertical axle biasing device having a portion connected to the frame and a portion connected to the axle assembly. Preferably, the ground engaging driving structures are wheels rotatably mounted on the axle assembly. However, small track assemblies may be used in place of the wheels. The axle assembly of each secondary driving assembly is movable in a generally vertical direction relative to the frame independently of the axle assembly of the other secondary driving assembly. The hydraulically powered motor of each secondary driving assembly drives its respective ground engaging driving structure. The axle biasing device of each secondary driving assembly biases its axle downwardly with respect to the track so as to maintain the ground engaging driving structures in ground contact while the vehicle drives over uneven terrain.
An engine assembly comprises a main engine (preferably an internal combustion engine) and a hydraulic pump unit operatively connected to the main engine. The hydraulic pump unit may include one or more hydraulic pumps and is fluidly communicated to both the hydraulically powered motors of the secondary driving assemblies and the hydraulically powered motor of the track assembly. The engine drives the hydraulic pump unit to supply pressurized hydraulic fluid to each of the hydraulically powered motors. The hydraulically powered motor of the driving track assembly moves the endless track using the pressurized fluid supplied from the hydraulic pump unit to affect a vehicle driving operation wherein the endless track engages the ground to drive the vehicle in the vehicle driving direction. Each of the hydraulically powered motors of the secondary driving assemblies operates the ground engaging driving structures using pressurized fluid supplied from the hydraulic pump unit so as to impart force to the vehicle. A steering device operatively connected to the secondary driving assemblies controls operation of the secondary driving assemblies so as to affect a vehicle steering operation wherein the ground engaging driving structures are operated to turn the vehicle with respect to the vehicle driving direction. Preferably, the force imparted to the vehicle by one of said wheels is greater than the force imparted to the vehicle by the other of the wheels, thereby causing the vehicle to turn with respect to the vehicle driving direction; although the wheels may pivot about generally vertical axes as in the '748 patent.
It can be appreciated that the ground engaging driving structures that flank the track in the vehicle according to this aspect of the present invention remain in ground contact while driving over the bumpy terrain as a result of the respective biasing devices always biasing the axles downwardly, forcing the respective driving structures into ground contact. When one flanking driving structure rides over a large bump, the driving structure riding over the bump moves vertically against the biasing of its biasing device and the other driving structure remains biased into ground contact by its biasing device. The track remains in full ground contact because the vehicle is not tilted. When one flanking driving structure rides over a minor rut or depression, the biasing device will bias the driving structure downwardly to maintain it in contact with the bottom surface of the depression (providing the depression is not excessively deep), thereby allowing the wheel to continue applying its tractive force.
Another aspect of the present invention relates to laterally adjusting the axle assemblies with respect to the vehicle track. This aspect of the present invention provides a vehicle comprising a main frame structure, a driving track assembly mounted with respect to the main frame structure, and a pair of secondary driving assemblies mounted on opposing lateral sides of the track assembly in flanking relation. The driving track assembly including an endless ground engaging track that extends in a vehicle driving direction.
Each of the secondary driving assemblies comprises a vehicle connecting portion connecting its associated secondary driving assembly on one of the opposing lateral sides of the track assembly, a driving structure mounting portion mounted to the vehicle connecting portion, a ground engaging driving structure mounted on the driving structure mounting portion, and a releasable lock. The driving structure mounting portion is movable generally inwardly towards or outwardly away from the track relative to the vehicle connecting portion. The releasable lock is movable between (1) a locked position wherein the lock fixes the driving structure mounting portion against movement with respect to the vehicle mounting portion and (2) an unlocked position wherein the driving structure mounting portion is movable relative to the fixed portion to thereby allow the driving structure mounted thereto to be repositioned inwardly towards or outwardly away from the track so as to change the lateral positioning of the driving structure with respect to the track.
An engine assembly supplies power to the track assembly and the secondary driving assemblies. The driving track assembly moves the endless track using power supplied from the engine assembly to affect a vehicle driving operation wherein the endless track engages the ground to drive the vehicle in the vehicle driving direction. Each of the secondary driving assemblies operates the ground engaging driving structures using power supplied from the engine assembly so as to impart force to the vehicle. A steering device is operatively connected to the secondary driving assemblies and controls operation of the secondary driving assemblies so as to affect a vehicle steering operation wherein the ground engaging driving structures are operated to turn the vehicle with respect to the vehicle driving direction.
This aspect is also particularly useful when harvesting row crops. By adjusting the lateral position of each ground engaging driving structure, the vehicle can be used for crops having rows of varying spacings and widths. In addition, the aspect of the invention can be advantageously used to provide the vehicle with additional stability by moving the driving structures laterally outwardly from the track.
Two additional aspects of the present invention relate to moving the ground engaging driving structures (which are preferably rotatable wheels) vertically with respect to the track. One of these aspects provides a pair of vertically respositionable axle assemblies with a wheel rotatably mounted to each. A vertical axle moving device for each axle assembly raises its respective axle assembly generally vertically so as to raise the wheel upwardly out of ground contact while the track remains engaged with the ground to thereby facilitate removal and changing of the wheel. In conventional tractors, a specialized jack is required to change a tire, which is rather expensive to obtain and it takes a relatively long period of time to complete the tire changing operation. This aspect of the invention simplifies the tire changing operation because no specialized equipment is needed to raise the wheel out of ground contact. The user simply activates the axle assembly to lift the wheel off the ground--the track still supports the vehicle and hence no jack or other specialized equipment is needed.
The other aspect of the invention relating to vertically moving the axle assemblies provides a pair of vertically respositionable axle assemblies each with a ground engaging driving structure mounted thereto. A vertical axle moving device is provided for each axle assembly and each moves its associated axle assembly downwardly so as to either maintain the driving structure in ground contact as it drives over a depressed area in the ground or to increase the ground bearing pressure the driving structure applies to the ground. This feature can be particularly useful when the vehicle is being driven over soft earth because the wheels can be pushed downwardly below the bottom of the track to provide extra traction. This feature is also particularly useful when driving along row crops because the ground in which the individual rows are planted is often higher than the ground between the rows. Using this feature, the vehicle can be driven with the track on the elevated portion where the crop is growing, and the driving structures engaged with the depressed portions between the rows. It should be noted that this aspect of the invention can be combined with the aspect of the invention concerning laterally adjustable axle assemblies to provide an effective base vehicle for harvesting row crops.
It should be understood that the vertical axle moving devices of the two aspects of the invention may be the same devices, although it is not necessary. Specifically, the present invention contemplates a vehicle wherein the vertical axle moving device moves the wheel out of contact with the ground to facilitate tire changing, but does not necessarily move the wheel downwardly to increase its ground bearing pressure or maintain it in contact with a depressed area of the ground. Conversely, the present invention contemplates a vehicle wherein the vertical axle moving device moves the axle assembly downwardly so as to either maintain its driving structure in ground contact or increase the ground bearing pressure of the driving structure, but does not move the axle assembly upwardly so as to raise the driving structure out of ground contact.
With either of these two aspects, it is preferred that the axle moving devices be operated using pressurized fluid from the hydraulic pump unit of the engine assembly. The flow of pressurized fluid to the axle moving devices can be easily controlled, and thus makes it suitable for use in conjunction with an electronic control module or other similar, inexpensive arrangement. With an electronic control module, suitable controls would be provided in the driver compartment to enable the driver to easily control the positioning of the ground engaging driving structures with respect to the track. However, the broad principles of the present invention are not intended to be limited to this type of arrangement.
A vehicle constructed in accordance with any aspect of the present invention may be adapted for use for farming, military, or any other application. For example, many conventional vehicles are currently used for military operations, including land mine detection and removal. The extensive use of land mines in recent years, particularly in civil wars and regional conflicts, has resulted in a very serious problem worldwide. At present, it is estimated that over one hundred and ten million mines are buried in seventy different nations. It is estimated that in Bosnia alone there are approximately 150 land mines buried per square mile. Land mines kill 8,000 to 10,000 civilians annually and maim many others, many of whom are children. The vehicles and the technology mounted thereon to detect and remove land mines are generally crude, slow, dangerous and generally ineffective.
One currently used approach to clearing land mines uses large cumbersome vehicles that plow or flail and beat the ground with chains to detonate hidden ordnance. This approach is expensive, can damage and scar the land and the application of this technique is restricted to open, level land. Another approach to clearing land mines entails using a detector system mounted to a conventional vehicle to locate the buried land mines and then retrieve them. These retrieval vehicles and the technologies associated therewith generally entail the use of crude tools that physically locate the hidden ordnance by poking the soil with unsophisticated probes. This approach is very time consuming and extremely dangerous. Other currently available detector systems are not widely used and are relatively ineffective because they generate a large number of false signals.
The conventional vehicles and associated technology currently in use for clearing land mines remove only about 100,000 mines per year at a cost of about $300 to $1,000 per mine. It is estimated that two million new land mines are deployed each year. It is clear that a new vehicle and new technologies and methods are needed for removing and destroying land mines.
To meet this need, a vehicle constructed in accordance with any aspect of the present invention may be adapted to suitably serve as the base carrier unit for such a vehicle. Specifically, the vehicle can be equipped with suitable electronic computing, sensing and communications equipment to construct a remote controlled and/or self-guided vehicle suitable for military applications, scientific or interplanetary exploration and other tasks in which direct human operation is undesirable or not available. The vehicle can be constructed to be capable of operation on land and underwater. Many military applications of the vehicle are contemplated, but the vehicle is particularly well suited for de-mining operations that utilize state-of-the-art technology.
When the vehicle is used for detecting and removing land mines, the vehicle platform is relatively small and is preferably operated by remote control. The vehicle's low center of gravity design and unique two wheel, one track structure enables the vehicle to traverse even the most difficult terrain.
A neutron activation analysis detection unit, for example, may be included in the vehicle; these analysis units are capable of quickly locating land mines and give few false signals. Depending on the level of support provided the vehicle, the vehicle could also be suitably equipped for accurately mapping the locations of buried mines in a minefield using a GPS (global positioning satellite) system or for remote operation using a combination of video and artificial intelligence to traverse a desired area or for automated destruction of located buried ordnance. The vehicle can also be provided with a radar sensor system to compliment the neutron activation analyzer. A plurality of carrier vehicles could be provided which comprise multiple robot units that are controlled by a central mobile command vehicle.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.